package com.dcivision.webdav.util;

/**
 * Encode an MD5 digest into a String.
 * <p>
 * The 128 bit MD5 hash is converted into a 32 character long String.
 * Each character of the String is the hexadecimal representation of 4 bits
 * of the digest.
 *
 * @author Remy Maucherat
 * @version $Revision: 1.1 $ $Date: 2003/08/13 16:39:44 $
 */

public final class MD5Encoder {

  // ----------------------------------------------------- Instance Variables

  private static final char[] hexadecimal = {
      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
      'a', 'b', 'c', 'd', 'e', 'f'};

  // --------------------------------------------------------- Public Methods

  /**
   * Encodes the 128 bit (16 bytes) MD5 into a 32 character String.
   *
   * @param binaryData Array containing the digest
   * @return Encoded MD5, or null if encoding failed
   */
  public String encode(byte[] binaryData) {

    if (binaryData.length != 16) {
      return null;
    }

    char[] buffer = new char[32];

    for (int i = 0; i < 16; i++) {
      int low = (int) (binaryData[i] & 0x0f);
      int high = (int) ( (binaryData[i] & 0xf0) >> 4);
      buffer[i * 2] = hexadecimal[high];
      buffer[i * 2 + 1] = hexadecimal[low];
    }

    return new String(buffer);

  }

}
